1. Field of the Invention
The invention relates to a semiconductor element, and more particularly, to an electrostatic discharge protection structure.
2. Description of Related Art
Electrostatic discharge (ESD) is a phenomenon of having a rapid flow of discharge via a discharge path within a short period of time after charges are accumulated on a non-conductor or an ungrounded conductor. For instance, human bodies, machines for packaging integrated circuits and instruments for testing the integrated circuits are all commonly known charged bodies, and when a charge body is in contact with a chip, it is possible to discharge to the chip. The process of discharging will generate several amperes of instantaneous discharge current within a period of time, which is as short as several hundred nanoseconds (ns), and thereby causes the integrated circuit in the chip to be damaged or invalided. Therefore, the integrated circuit of the chip is generally configured with an electrostatic discharge protection circuit to prevent the electrostatic discharge phenomenon from damaging the internal circuit.
FIG. 1 is a conventional configuration diagram illustrating a use of an electrostatic discharge protection structure to protect an internal circuit. As shown in FIG. 1, the design of the electrostatic discharge protection circuit 100 must consider all the possible electrostatic discharge paths, so as to protect the internal circuit 110. Therefore, electrostatic discharge protection structures 112 must be disposed between an input pad 102 and a power pad 106, between an output pad 104 and the power pad 106, between the input pad 102 and a ground voltage, between the output pad 104 and the ground voltage, and between the power pad 106 and the ground voltage.
In general, a breakdown voltage of the electrostatic discharge protection circuit will be lower than a breakdown voltage of a main circuit. However, in different circuits, breakdown voltages required by the electrostatic discharge protection elements may be different. Therefore, how to design an electrostatic discharge protection circuit capable of adjusting a breakdown voltage thereof in compliance with the requirements of various circuits has become a major issue for current research.